Liquid crystal displays use mixtures of liquid crystals having desired material properties such as operating temperature range, thermal stability, light stability, switching time, and contrast ratio. The properties of the mixtures and devices are determined by the constituents of the mixtures.
The demand for liquid crystal displays having improved performance has increased. In particular, liquid crystal mixtures having low threshold voltage are desired, especially for display applications. The threshold voltage is the amount of voltage needed to apply across a pixel to produce a response. Addressing pixels with lower voltages allows simplification of the electronics used, resulting in the possibility for space and weight savings. The threshold voltage is inversely proportional to the dielectric anisotropy of the mixture. Therefore, one way to produce a liquid crystal mixture having a low threshold voltage is the use of mixtures having a large (positive or negative) dielectric constant.
U.S. Pat. No. 5,759,443, U.S. Pat. No. 4,873,019, CN 1928001A, and EP patent application EP0789067A1 disclose certain compounds having cyclopentyl groups.
There is a continuing need in the art for improved liquid crystal compounds and mixtures.